Separating material for molds



UNITED STATES PATENT OFFIQE.

JOHN B. JONES OF ATLANTIGGITY, NEW JERSEY.

sErAnA'rinG MATERIAL ron MOLDS.

No Drawing.

To all whom it may concern.-

Be it known that 1, JOHN B. Jones, a citizen of the United States, and resident of Atlantic City, in the county of Atlantic and State of New Jersey, have invented certain new and useful Improvements in Separating Materials for Molds, of whichthe following is a specification.

My invention relates to molds adapted to be used by dentists and others, and pertains more particularly to materials for application to the surface of the mold to facilitate separation of the cast therefrom.

As is Well known, plaster of Paris, cement, concrete, and like materials are used in casting, in many instances for both the mold and the cast formed therein. Plaster of Paris is commonly used by dentists for taking an impression of the teeth and interior of the mouth and for forming the mold in which the cast is made, the cast material also generally being plaster of Paris or some similar material. Due to the fact that the mold and cast materials are of the same nature and possessed of rapid-hardening qualities, considerable difiiculty has been experienced inseparating the mold from the cast after the casting operation, without injury to the latter. Similar trouble has been found in the use of molds of cement, concrete and like matedestroyed and the cast exposed to the danger of injury by the cutting operation.

To render it possible to separate the mold from the cast more readily and enable the mold to be used repeatedly the surface of the mold has been coated with various materials designed to present a well-defined line of demarcation between the mold and the cast and to render the surface of the mold smooth, so that the material of the cast might not adhere thereto, but be easily separable therefrom after the cast material had set.

One method hitherto employed was to apply to the interior surface of the mold a coating of oil, usually superposed upon a coat of shellac or other substance. This process required two distinct applications of separating materials, and since the oil coating could not be applied until the shellac was thoroughly dry and hard, its use involved more time than where a single coat is applied and thus delayed the casting operation.

Specification of Letters Patent. -Patented Fe}; 14, 1922 Application filed December 24, 1920. Serial No. 433,031.

The coat of oil is not only inconvenient. but is also disagreeable to the operator, being sticky or gummy and soiling both the cast and the hands of the operator or user.

Other materials have been used, principally in alcoholic solution, but these are unsatisfactory on account of the present high cost of alcohol and for the reason that alcohol evaporates so rapidly that a separator material containing it cannot be handled so conveniently and will not retain its original condition orconsistency for so long a period as a material in which no alcohol or other rapidly-evaporating agent is present.

The objects of my invention are to overcome these disadvantages and provide a separating material that is convenient to handle and easy to prepare and apply, that can be produced at comparatively low cost without the use of alcohol or similar agents. that is not sticky and will not injuriously affect either the mold or cast or the hands of the user, that will retain its proper or desired condition more satisfactorily and for a longer time than materials containing alcohol, ether, or other highly volatile agents, and that will permit the cast to be easily and quickly separated from the mold.

The composition I employ to attain these beneficial. results consists of shellac in an alkaline solution, the alkaline substance being preferably borax. In preparing the composition, the borax and shellac are preferably powdered and mixed in the proper proportions, in which condition they are in convenient form to be supplied to the trade. A mixture of approximately equal parts of borax and shellac gives good results, but the proportions may be varied somewhat. The preferred mixture consists of approximately .535 grains of borax and 580 grains of shellac.

To prepare the mixture for use, it is dis solved in clear hot water, preferably in the proportion of about two'parts of the mixture to ten parts of water, 1100 or 1200- grains of the mixture being dissolved in approximately one pint of water. The Water should not be boiling, but considerable latitude may be had. in regard to the water temperature. The mixture of borax and shellac is poured slowly into the hot water and stirred until all of the mixture is dissolved. By this process an aqueous solution of borax is obtained, in which solution the shellac is dissolved to form an alkali salt of resin, in the nature of a resin soap.

When cool, the substance is ready for use and may be applied to the mold with a brush, by immersion, or in any other convenient or suitable manner. The coating thus formed gives to the mold a smooth, hard surface,

of such coloring matter is, however, not essential and forms no part of my invention.

I claim:

1. A separating material for plaster casts and the like which consists of shellac dissolved in an aqueous solution of borax.

2. A separating material for plaster casts and the like which comprises shellac, borax and Water, in approximately the proportions of 535 grains of borax and 580 grains of shellac to one pint of Water.

3. A separating material for plaster casts and the like which consists of approximately equal parts of boraX and shellac dissolved in Water. 7

In testimony whereof I afiix my signature.

JOHN B. JONES. 

